Detectives searching through the debris of the Monday morning explosions at two Montgomery County medical clinics found evidence of two bombs placed on the outside wall of one of the clinics, police said yesterday.

Meanwhile, the staff and patients at an abortion clinic in Silver Spring were evacuated yesterday after the false report of a bomb, police said.

Sgt. Harry Geehreng, spokesman for the Montgomery County Police Department, said the bombs Monday had been placed at ground level outside the office of the Planned Parenthood family planning center in Rockville.

The remains of the bombs and other debris from the building have been sent to the fire department laboratory to determine their make-up and whether any other devices were used, officials said.

Meanwhile, the Planned Parenthood clinic remained open for business today. A makeshift examining room was set up in one of the conference rooms because all of the building's windows had been shattered by the blast.

The second and more heavily damaged clinic, the Metropolitan Medical and Women's Center in Wheaton, has moved into the office of a private physician, said Gail Frances, a spokeswoman for the clinic. Clinic officials hope to reopen the building in about two months.

Abortions are performed at the Wheaton clinic and the Planned Parenthood center counsels women on methods of contraception, including abortion referral.

"Morale is very high," said Frances. "We've had tremendous community support" from pro-choice groups.

No one was injured in the predawn blasts, the latest in a growing number of attacks against medical facilities that either provide counseling or perform abortions.

A bomb threat was received yesterday at 12:25 p.m. at Alternatives, Inc., at 1805 Cameron St. in Silver Spring, according to police. Following the evacuation, the building was closed for the day. Police found no bomb.

Police and fire officials said they had no suspects in any of the incidents and that no group or individuals have claimed responsibility.