Dannemora Schools on High Alert After Murderers Escape from Prison

— -- Schools in the small upstate New York town of Dannemora are on high alert and taking extra precautions after two convicted murderers escaped from the town's maximum-security prison.

Fear started to spread Saturday morning in the town, about 20 miles south of the Canadian border, after inmates Richard Matt and David Sweat were reported missing from the Clinton Correctional Facility.

On Sunday, officers searched all of the schools, buses and surrounding woods and swamps, according to a letter from Saranac Central School District Superintendent Jonathan Parks.

New York State Police officers were stationed at all schools in the district, Parks' letter said, and outdoor activities at the schools were cancelled.

Bus drivers have also been instructed to wait for students who want to stay inside their houses until their bus arrives in the morning, the letter said.

Matt and Sweat escaped through holes in the wall of their adjoining cells, officials said. They made their way onto a catwalk about six stories high, then climbed down and emerged onto the street through a manhole cover.

Authorities have expanded the investigation to Canada and Mexico. About 300 leads have been developed so far in the search for Matt and Sweat, State Police said.

New York Gov. Andrew Cuomo has urged anyone with information to come forward.

"This was the first breakout [at the prison's maximum security portion] since 1865 and I want to make sure that it's the last," Cuomo said.

Matt is described as standing 6 feet tall, weighing 210 pounds and having black hair and hazel eyes. He has tattoos reading "Mexico Forever," a heart on his chest and left shoulder, and a Marine Corps badge on his right shoulder, police said. Sweat is described as 5 foot 11, weighing 165 pounds and having brown hair and green eyes. He has tattoos on his left bicep and his right fingers, police said.

New York State is offering a $100,000 reward for information leading to Matt and Sweat's apprehension and arrest.

ABC News' Brian Hartman and Gio Benitez contributed to this report.