Houston is now 'mostly dry' following historic flooding caused by Hurricane Harvey, mayor says

— -- Houston Mayor Sylvester Turner said Thursday that the city is now "mostly dry," after having taken an aerial tour of the city.

The two areas still dealing with flooding issues are Kingwood and West Houston, Turner said.

Six days after Hurricane Harvey roared ashore in southeastern Texas, officials and residents have begun to assess the storm's trail of destruction in Houston as the flood waters slowly started to recede.

First responders, as well as urban search and rescue teams, launched a block-by-block, door-to-door search of badly flooded areas of Houston today to conduct recovery operations now that the weather has cleared and the rain has finally stopped.

On Thursday, the Houston Fire Department had received 800 service calls, but only 22 were water-related, a spokesperson said. Since the operation began, the fire department has received about 16,000 service calls, about 7,600 of which were water-related.

Police had participated in three rescues in high water between 6 p.m. Wednesday and 11 a.m. Thursday, a spokesperson said Thursday. Officers are still searching for 19 people who were reported missing, the spokesperson said.

Gov. Greg Abbott also announced late on Thursday he would be easing restrictions on fuel supplies -- via a waiver of the International Fuel Tax Agreement -- in order to "reduce the cost and administrative burden getting these critical supplies across state lines." There were lines of cars waiting at gas pumps for blocks even in Dallas, which was relatively spared by the storm, according to The Associated Press.

"As Texas begins the recovery process in the wake of Hurricane Harvey, it is important that Texans have access to much needed resources, including gasoline and fuel," Abbott said in a statement. "Texans should rest assured that their state government is doing every possible to ensure the accessibility and affordability of the necessities allowing us to focus on the process of rebuilding together after this storm."

The number of people in shelters is going down, Turner said. By the end of Friday, the people at the Toyota Center will be transferred to the George R. Brown Convention Center.

The Toyota Center had been opened as a result of overcrowding at the convention center, which housed 10,000 people at its peak. Less than 8,000 people are currently at the convention center, Turner said. There are still 37,000 homes in the area without power.

Police have arrested 69 people total, eight of whom were arrested for looting, they said.

One year from now when people visit Houston, they will not see signs of Harvey, Turner said.

"The Astros are playing baseball..." Turner said. "The city of Houston is open for business."

The BARC animal shelter and Houston Zoo will reopen Friday, Turner said.

Houston Independent School District Superintendent Richard Carranza said that every single one of the 200 of the school district's facilities that have been inspected have been touched by floodwater. Officials hope to have facilities in shape by Sept. 8 and to re-start school on Sept. 11, Carranza said.

The school district has 218,000 students, 31,000 employees and 300 facilities, Carranza said.

Harris County Judge Ed Emmett told ABC News on Wednesday that thousands of people likely remain stranded and an estimated 30,000 to 40,000 homes have been destroyed in the Houston area as a result of Harvey's torrential rains, flooding and strong winds. At least 39 people have died as a result of the storm's wrath, according to The Associated Press.

Preliminary data shows Harvey has broken the rainfall record for a single storm event in the lower 48 states, according to the National Weather Service. The storm dropped a preliminary tally of 51.88 inches of rain in Cedar Bayou, Texas, some 30 miles east of Houston.

Harvey, which first hit land as a Category 4 hurricane, made its third landfall just west of Cameron, Louisiana, early Wednesday morning as a tropical storm. Harvey weakened to a tropical depression overnight before being degraded to a low-pressure system that is expected to bring heavy rain to the Tennessee Valley and the Ohio Valley.

As Harvey left the Houston area, the city's busy George Bush Intercontinental and William P. Hobby airports have reopened and officials anticipate all airlines to gradually resume service in the coming days.

The ports of Houston, Texas City, Galveston, and Freeport have partially reopened with specific restrictions on vessel sizes and traffic, according to the captain of the port for the Coast Guard Sector Houston-Galveston.

The Mexican Red Cross sent a convoy of English-speaking volunteers to Houston on Wednesday, hours after Texas Gov. Greg Abbott announced the state will accept the Mexican government's offer of aid and relief supplies, including vehicles, boats, and food.

Meanwhile, evacuees at overcrowded shelters were transported to a newly-opened emergency shelter at the NRG Center in Houston, which can house 10,000 people. According to the Federal Emergency Management Agency, there are three "mega shelters" in Houston and one in Dallas currently housing evacuees and flood victims.

The federal government still has more than 12,400 personnel stationed across Texas and Louisiana in response to the storm and subsequent flooding. FEMA Administrator Brock Long told reporters this morning that the agency's primary mission is still "taking care of people" and restoring "hope."

Some 10,000 people have been rescued in affected areas by federal forces, along with countless volunteer and neighbor-to-neighbor rescues, Long said.

Approximately 325,000 people have registered for FEMA assistance and $57 million has been distributed so far, according to Long. He reiterated that the agency will first try to move displaced residents from shelters into local hotels before helping them muck out their flooded homes so they can return to them. FEMA has already placed more than 1,800 flood survivors in hotels, Long said.

The U.S. Northern Command has deployed about 6,300 active-duty military personnel to the affected areas who have rescued or assisted more than 1,200 people so far.

As of this afternoon, the Coast Guard has rescued more than 9,000 people and 1,000 pets, with search and rescue operations ongoing.

The Transportation Security Administration has deployed nearly 700 additional employees to the Houston area, 300 of whom will fill in for TSA officers at local airports who were impacted by the storm, while the other 400 will serve on FEMA's Surge Capacity Force.

ABC News' Jeffrey Cook, Erin Dooley, Max Golembo, Elizabeth McLaughlin and Crystal Muguerza contributed to this report.