Early tests show the air is safe to breathe after a fire destroyed a Mount Vernon chemical warehouse, spurring authorities to evacuate surrounding blocks and tell nearby residents to close windows and stay indoors, firefighters said.

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

Tests continued as firefighters searched for any smoldering areas remaining after Friday night's four-alarm blaze. The fire spread to two other buildings in the largely industrial neighborhood around the South Fulton Avenue building, but no injuries were reported.

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

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 had been blowing in the direction of neighboring Pelham, and the department was advising 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 tow-truck 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 Red Cross stood ready to help residents if the area was declared unsafe, said John Rabitz, chief executive officer of the organization's Westchester County chapter. The Red Cross was running a canteen for the fire, police and other emergency workers, he 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.

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.

KEM Chemical specializes in supplying acids and other chemicals for microelectronics manufacturers, according to its Web site. The 47-year-old business is a relatively small player, often producing chemicals in volumes smaller than the manufacturers want to make for themselves, the Web site says.

A call to the firm's telephone yielded a busy signal Friday night, and an e-mail message to company representatives was not immediately answered. No home telephone number could be found for the company's chief executive.

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