A five-block area of a warehouse district was evacuated for several hours early Monday due to poison leaking from a barrel at a trucking company, the fire department reported.

Ten to 15 gallons of mercaptoethanol, a mild poison, leaked from the barrel being shipped by space contractor Morton Thiokol at the Roadway Express Truckline dock, causing the emergency, said Gerald King, a police dispatcher.Carol Kessinger, a fire department spokeswoman, said the poison was dangerous only if absorbed through the skin. One man handling the barrel was splashed with the chemical and was treated and released at Vista Hills Hospital.

The leak was discovered at 2:34 a.m.

"They've evacuated a couple of buildings, and they're cleaning it up," Kessinger said.