"Now, on Twitter, I can find information about places where they're fighting," said Hernandez. "I can see blogs posted the same day."
"Once we get the information there, we send Tweets, texts or call whomever we care to inform," Mendez said.
Reynosa residents also use YouTube. A video posted in early March shows seven minutes, uncut, of a drive through the streets of Camargo, a border town just west of Reynosa, with a woman's voice narrating. Littered with charred vehicles and postwar remnants, the streets are patrolled by military personnel holding heavy weaponry. The woman hides the camera as she passes Mexican soldiers.
"It is remarkable to me, the value of some citizens who dare to document these facts," said Hernandez.
Authorities in Reynosa complain that residents' Tweets and YouTube videos are creating a sense of paranoia and "psychosis" by spreading rumors and inaccurate information virally.
"Their information is not precise. We cannot verify the information that the personal Twitter accounts post," Juan Triana Marquez, a director of the Reynosa city government, told ABCNews.com. "We can verify our information with the police department."
Nevertheless, the lack of media and need to get out what they see as accurate information has sparked local authorities to open their own Twitter account.
"We know that the people need information because of the current situation," said Marquez, who updates the city's Twitter account.
Local and state authorities have been subject to attacks from cartels including grenades and combat-style ambushes. The Twitter account lets citizens know where and what they are responding to. Their account, @dirdegobreynosa, has more than 2,100 followers.
So it was the authorities who, after an explosive device was found under a bridge, Tweeted, "#Reynosa – Situation of risk in the area of Col. Achilles Serda, Plaza. Unexploded ordinance. TAKE PRECAUTIONS."
On May 5, authorities Tweeted this after a firefight broke out on in the Rio Bravo subdivision of the city.
"There is a risk in Rio Bravo. Please do not create confusion. Road to Rio Bravo closed. #Reynosa
Authorities say three men were killed in the shootout between Mexican soldiers and armed civilians.
Around the world, Twitter has become a means of relaying and sharing information among groups of people subjected to violence and oppression.
"We've seen examples, from the Red Cross during the Haiti crisis using Twitter, all the way to the Red Shirt movement in Bangkok, Thailand, using Twitter to organize protests and drive support," said Kyle Lacy, CEO of Brandswag and author of "Twitter Marketing for Dummies."
"I think the biggest example we have seen is in Iran during the Green Revolution," added Lacy. "When the government cracked down on Internet use, the people took to Twitter mobile to send tweets of the crackdown and violence used towards protestors. People even began to put up green icons on their profiles to show support for the campaign."
According to Lacy, the ease of Twitter compared with some other social networking websites is the reason we see Twitter use pop up during crisis situations abroad.