Federal prosecutors and D.C. police are investigating an alleged ring of California pimps who are bringing teen-aged prostitutes into the city, according to informed sources.

The case could involve an umprecedented business alliance among pimps, usually a highly competitive profession, sources said.

Several teen-agers have testified before a federal grand jury in recent weeks and 10 men have been identified as suspects in the alleged ring, the sources revealed.

"These men round up girls who are runaways or escapees from institutions, and they hang around high schools and pick up unhappy girls," said one source familiar with the investigation.

"They put them out on the streets of California to see how they'll do then they bring them here to get away from their ties at home. We're trying to get them to the grand jury before they lose all respect for themselves, while there's still some posibilities that they'll tell what happened to them."

The suspected pimps' operation is a semi-sophisticated business with the partners taking turns as overseers and sharing profits, according to sources.

Previous pandering cases have involved pimps operating independently. Police have identified about 500 suspected pimps who have worked in Washington recently.

The federal probe centers on possible violations of the Mann Act, which deals with transporting women across state lines for purposes of prostitution. The investigation is the latest phase in the most intense law enforcement effort against pimps here in recent memory.

A Superior Court special grand jury has been meeting five weeks to consider evidence against suspected pimps here. Police have presented each prostitute arrested for a first offense to the grand jury and about 10 of the 35 have provided information about their pimps, according to informed sources. This grand jury investigation has focused on six to eight local pimps, sources said.

Creation of the grand jury stemmed from an inncident last month in which a young prostitute attempted to tell Judge Luke C. Moore about her pimp and Moore was told by U.S. attorneys that prosecutors needed the testimony of two people to make a pandering case.

Prosecutors here have long regarded prostitution and pandering as unattractive cases. Witnesses lie, change their minds and fail to show up, and judges tend to deal leniently with defendants.

As a result of the lack of stiff penalties, police believe Washington has become a mecca for prostitutes and pimps. The women are concentrated downtown, along 14th Street NW from Florida Avenue to L Street, and west on K and L streets to 15th Street.