A frantic search for four stolen Impressionist paintings led to a most unlikely place: the parking lot of a mental hospital just a few hundred yards from the scene of the crime.

There, in the back seat of an unlocked car, a painting by Claude Monet and another by Vincent van Gogh were found Monday in perfect condition, authorities said Tuesday.

The paintings, worth $64 million combined, were still under the display glass used by the private museum from which they were stolen in a Feb. 10 armed robbery, museum director Lukas Gloor said.

"I am incredibly relieved that two paintings have returned," Gloor said. "We're very happy that both the paintings are in absolutely impeccable shape."

The other two paintings taken from the E.G. Buehrle Collection — by Paul Cezanne and Edgar Degas — remain missing, police said. Together, the four paintings are worth an estimated $163 million.

Art experts have suggested that the robbers took advantage of what appeared to be an easy mark — a low-security museum — without knowing much about art or how difficult it can be to sell such well-known works.

"The robbery was not done with knowledge about art," Gloor said.

The robbers took the first four paintings they came across when they raided the museum shortly before closing on a Sunday afternoon. Although they managed to take the most valuable painting in the collection — Cezanne's "Boy in the Red Waistcoat" — they passed over the second-most valuable picture, another Cezanne.

Gloor said he suspected the robbers abandoned the two paintings, which were the largest of the four, because their size complicated transporting them.

They were discovered Monday on the back seat of a white sedan in a parking lot in front of the University Psychiatric Clinic. It was not known how long the car had been there, police said.

An employee of the clinic making a routine check of the lot noted the car because it was unlocked. Police immediately sealed off the area, examined the car and hauled it away.

Police had said initially that a white vehicle might have been used by the three robbers when they made their escape. The clinic is about 500 yards from the museum.

The recovered paintings — Monet's "Poppy field at Vetheuil" and van Gogh's "Blooming Chestnut Branches" — will be returned to the museum in the coming days, Gloor said.

"But we must not forget," he added, "that two more paintings of our collection are still missing, including our collection's landmark 'Boy in the Red Waistcoat."'

That painting alone is worth $91 million. The other missing painting is Degas' "Ludovic Lepic and his Daughter," worth $9 million.

"The most valuable one and the least valuable one are still missing," said Gloor.

Zurich police spokesman Marco Cortesi said the clinic employee who found the paintings would get a part of a $90,000 reward. He said the exact amount has yet to be determined.

Asked whether a ransom had been paid for the paintings, Cortesi said, "It is unknown whether a sum of money has moved." Gloor, standing next to him, said, "I can't give any information on that."

Interpol, which has been coordinating the international search for the paintings, said it was unable to comment on any developments because that would be up to Swiss authorities.

"Connections with other arts thefts in the country and abroad are being examined," said Cortesi.