By APRIL CASTRO Associated Press Writer

AUSTIN (AP) - Charges have been dismissed against a third man accused in the strangulation and shooting deaths of four teenagers at an Austin yogurt shop 11 years ago.

Maurice Pierce was released from custody Tuesday, but authorities said the case would remain open.

"It is without pleasure that I announce today that the yogurt shop capital murder cases against Maurice Pierce have been dismissed," Travis County District Attorney Ronald Earle said.

Pierce had been awaiting trial since police arrested three suspects in October 1999.

Officials said in a news conference that they did not believe they could convict Pierce without reasonable doubt.

Michael Scott was given a life sentence in September for the murder of 13-year-old Amy Ayers at an I Can't Believe It's Yogurt Shop the night of Dec. 6, 1991.

Another defendant, Robert Springsteen, was sentenced to die by lethal injection for Ayers' slaying.

A grand jury failed to indict a fourth man, Forrest Welborn.

Springsteen and Scott were the primary witnesses against Pierce and "neither is currently available to testify," Earle said. Each of them has a 5th Amendment right not to testify.

"Both have made statements that cannot be used without violating the constitutional right of Maurice Pierce to confront the witnesses against him."

Scott's wife, Jeannine Scott, who maintains that her husband is innocent, said he refused to testify in Pierce's case.

"I know Michael told them no. I would imagine Robert told them no," she said. "It's not a matter of not being available, it's a matter of not wanting to help them convict another innnocent person."

Also killed were Eliza Hope Thomas, 17, and sisters Jennifer and Sarah Harbison, ages 17 and 15, at the shop where two of the girls worked.

The store was robbed, and the victims were bound, gagged and shot in the head. The store was set on fire.

Earle said the case has no statute of limitations.

"We do not have the evidence to convict him right now, but life is long," Earle said. "We believe there are people who know something that would be helpful in this investigation. We urge them to come forward. They will have an attentive audience."