COLOGNE, West Germany (AP) _ Two aging chimpanzees, who may have been suffering from stress and fear at being alone in a monkey house, attacked and seriously injured the Cologne Zoo director Thursday, authorities said.

Director Guenter Nogge was taken to the hospital with serious bite and scratch wounds, police said. Authorities shot and killed the chimps, both of which were about 30 years old.

Authorities said the chimps attacked a 19-year-old keeper who had entered their cage. The keeper sounded an alarm after the two animals escaped and started running through the monkey house.

Zoo officials immediately cleared the public away from the facility.

Nogge entered the monkey house and tried to calm the chimps after they had re-entered their cage, the police statement said. The animals attacked the 41- year-old director before one of the chimps was shot by a zoo guard.

The second chimp ran out of the monkey house and stopped at the entrance to a cellar of a nearby building, where it was shot by police.

Zoo officials said that because of their age, the two chimps were not moved to a newly constructed monkey house, and that they were the only animals left in the old facility. The officials said fear and stress may have led to the attack