Investigators studied autopsy reports and photos Friday but were unable to determine whether seven slain women, most of them prostitutes, were victims of a single serial killer.

The bodies of the women, either dumped along highways or near creeks, were discovered between July and January in Oklahoma, Arkansas, Texas and Mississippi.

Though more than 60 investigators from six states and 17 agencies met for six hours to compare notes to see if a single killer might be responsible — perhaps a long-haul truck driver preying on truck-stop prostitutes — the law enforcement officials appeared to be no closer to solving the cases.

"We can't say at this time that it's one person who did this," said Jessica Brown, a spokeswoman for the Oklahoma State Bureau of Investigation (search). "We have no suspects at this time. We really need the public's help."

No further meeting was planned.

Six of the victims were prostitutes; the seventh hasn't been identified. Four were from the Oklahoma City area. At least four were last seen at truck stops, and at least three were strangled. Most of the bodies were nude.

The women who were identified were Patsy Laverne Leonard, Casey Jo Pipestem, Sandra Beard, Jennifer Hyman, Margaret Gardner and Sandra Richardson.

Five Lawton-area killings were initially classified along with the seven, but those cases have been determined to be different enough to be treated as a separate group, Brown said. She said she could not elaborate.

None of the law enforcement officials except Brown was available for comment after the meeting, which was closed to the public.

These will be difficult cases to solve, Brown said earlier.

"These victims didn't stay in one place long," she said. "People don't necessarily recognize them. A lot of these victims did not have tight relationships with their families. A lot of times, families help us solve crimes."