PELHAM -- A blaze at a chemical warehouse spurred authorities to evacuate surrounding blocks, halt a high school play and tell nearby residents to shut windows and stay indoors.

Air-quality tests and checks for any hazardous material oozing from the collapsed KEM Chemical Corp. headquarters in Mount Vernon found no dangerous contamination as of early Saturday, according to authorities.

Firefighters drenched the rubble of the two-story building after Friday night's four-alarm blaze, which spread to two other buildings in the largely industrial neighborhood. A fire captain was treated and released from a hospital after twisting a knee at the fire scene; no other injuries were reported, firefighters said.

Investigators have not determined what caused the blaze.

A preliminary report indicated that hydrochloric acid, nitric acid, sulfuric acid, alcohol and acetone might have been among the chemicals in the warehouse when it caught fire, the Fire Department said.

Firefighters were told that some of the warehouse's chemicals would react with water. But "really, we had no choice but to put lots and lots of water on it," Fire Chief Al Everett told The Journal News.

Workers and the few residents within a three-to-four-block radius of the building were told to evacuate, and the area was cordoned off, firefighters said. Smoke from the fire blew in the direction of neighboring Pelham, and the department initially advised residents there to remain inside and shut their windows.

Flames shot 15 to 20 feet from the warehouse roof, said witness Peter Tsachalis.

"It was going pretty intense," said Tsachalis, who owns a business and a couple of rental homes directly behind the chemical supplier. His four tenants and their two pets got out safely, and firefighters kept the fire from spreading to his property, he said.

The warehouse collapsed like a house of cards after the roof fell in, driving the second story into the first floor and the first floor into the basement, firefighters said.

In Pelham, the fire forced an abrupt end to a student production of "Hello, Dolly!" Police came into Pelham Memorial High School auditorium and stopped the play, telling everyone to leave because of the fire, said Pelham schools spokeswoman Angela Cox.

"They said it was a precaution. Everybody got out safely," she said.

The risks to nearby residents, if any, were unclear. In general, inhaling the acids can irritate the nose, throat or respiratory system, according to the federal government's National Institute for Occupational Safety and Health. Inhaling acetone, a common component of nail polish remover, can also cause dizziness or headaches, the institute says.

A phone call to KEM Chemical rang unanswered early Saturday, and an e-mail message to company representatives late Friday was not answered. No home telephone number could be found for the company's chief executive.