(CNN) -- A massive fire broke out after a train derailed Friday night in northeastern Ohio near the Pennsylvania state border, leading officials to issue evacuation and shelter-in-place orders for nearby residents.
No injuries were reported after the derailment in East Palestine, about 15 miles south of Youngstown, Mayor Trent Conaway said during a Friday night news conference.
On Saturday, he issued an emergency proclamation, saying the town had been "threatened" by hazardous materials potentially released in the accident.
The proclamation noted a Norfolk Southern train derailed Friday night.
"As of right now air quality, even one street back is OK," he said. The smell in the air is because of the fire, he said, but there are no concerns about air quality.
The derailed train derailed had more than 100 cars, according to the National Transportation Safety Board.
About 50 of them were involved in the derailment -- 20 of which contained "hazardous materials," NTSB board member Michael Graham said during a Saturday afternoon news conference.
"Four tank cars carrying vinyl chloride were involved in the derailment and were exposed to fire," Graham said.
One car released some of the vinyl chloride through a safety release valve, Graham said. State environmental officials say they have not detected any harmful levels of the chemical in the community.
He added there was still an "active fire scene," and could not estimate when the flames would be put out.
The cause of the derailment was not known Saturday.
Investigators say the train had image and data recorders onboard. It will take four to six weeks for the NTSB to have a preliminary report on the accident, Graham said.
EPA: No harmful levels of compounds in air
No harmful levels of compounds have been detected in the air as of Saturday evening, a spokesperson with the Ohio Environmental Protection Agency told CNN in an email.
"Ohio EPA will remain on site and air monitors will remain in place as long as necessary," Ohio EPA spokesperson James Lee said in a statement. "Ohio EPA has established containment to help limit any damage to local streams and rivers from water runoff from the firefighting."
The agency will work with local officials and the railroad company to "identify the nature and extent" of any possible contamination and will work to ensure cleanup efforts to protect human health and the environment, Lee said.
A shelter-in-place order issued
Officials issued a shelter-in-place order for the entire town of roughly 5,000 people, while an evacuation order was in effect within a mile of the train crossing at James Street as of early Saturday. Conaway said he did not know when those orders would be lifted.
Two evacuation stations have opened to provide shelter to residents, and the Red Cross has been notified, Conaway said.
Conaway on Saturday called for the "exercise of all necessary emergency authority for protection of lives and the property of the residents of the Village of East Palestine, Ohio."
The proclamation also called on citizens to comply with the emergency measures.
Traci Spratt, the interim manager of the village of East Palestine, said Saturday an evacuation order for a one-mile radius from the incident remained in place "until further notice," and stressed "we need everyone to stay away from the scene."
Spratt also identified the chemical burning as vinyl chloride and said officials were conducting "continuous air monitoring and have found zero health risks."
"The village's drinking water is safe to drink and is being continually monitored," Spratt added.
Photos from the scene showed a large, dense cloud of smoke engulfing flames atop the train. Firefighters from three states, Pennsylvania, Ohio and West Virginia responded, according to Conaway.
The Norfolk Southern train departed from Madison, Illinois, and was bound for Conway, Pennsylvania, when it derailed, according to the NTSB.
Norfolk Southern Railway said in a statement it is aware of the derailment and was "coordinating closely" with local first responders while mobilizing their own teams.
"We will share more details as they become available," the statement said.
CNN has reached out to Norfolk Southern for further comment.