HOUSTON -- The Houston Police Department and the FBI asked for the publics help Wednesday in locating several potential witnesses in the apparent abduction of Laura Ayala.

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Laura, 13, disappeared on March 10 from the parking lot of a Conoco gas station, 2610 Broadway, in southeast Houston.

Police said that she had gone to the store to buy a newspaper for a school project and when she did not return, her mother became concerned and went looking for her. The newspaper and Laura's shoes were found in the street, authorities said.

During a news conference Wednesday, investigators said that Laura may have been taken by bus to Reynosa, Mexico.

Police said that they learned that an El Expreso Bus Co. bus left Houston between 10:30 and 11 p.m. on March 13 with 13 passengers on the overnight trip to the Rio Grande Valley area in South Texas.

The bus driver from that evening told investigators that he believes the first group of passengers consisted of an adult male and female, as well as a young child who fit Laura's description, authorities said.

"He believes that the girl on that bus does match the description of Laura," Houston Police Detective J. Sosa said. "He's not 100 percent positive, but he strongly believes that it could be her."

The bus driver described Laura as wearing a pink top and dark jeans at the time, authorities said.

Police said that bus records indicate that one of the tickets was purchased under the name of Laura A.

The clerk who sold the tickets at the Main Street terminal does not remember who purchased the tickets but did confirm her habit of only using the first initial of the last name for several of the passengers, police said.

The bus company does not collect any other identifying information on its passengers, authorities said.

The bus made three stops in the Rio Grande Valley in the cities of McAllen, Edinburg, and Hidalgo.

Police said that a second bus line took the trio on to Mexico.

The Noreste Bus line does confirm that three passengers from Houston transferred to a 6 a.m. bus to Reynosa on March 14, authorities said.

Investigators said that they consider this an unconfirmed sighting of Laura and would like the public's help in locating any of the 12 passengers on the bus that night, including the couple that may have been with her.

The two people named on the one-way tickets as traveling with Laura were Virginia Ramirez and Julio Barrios, authorities said.

Police described Ramirez as being in her mid 30s, about 5 feet 5 inches tall, weighing 120 pounds, wavy shoulder length hair, and wearing a light blue dress.

Barrios was described as being in his mid 40s, 5 feet 8 inches tall, weighing 160 pounds, with salt-and-pepper hair, a mustache, and wearing a white T-shirt and blue jeans.

The other passengers and their final destinations are as follows:

• Jose C. Lira -- Hidalgo
• Martha L. -- Hidalgo
• Jose Lira -- Hidalgo
• Juliana L. -- Hidalgo
• Eunice Leija -- Edinburg
• Edith Leija -- Edinburg
• Javier Pacheco -- McAllen
• Saul Gonzalez -- Hidalgo
• Carolina Candanosa -- McAllen
• Jesus Z -- McAllen

In addition to the continuing investigation in the Houston area, FBI and U.S. Border Patrol agents in McAllen are receiving assistance from authorities in Mexico.

A $19,000 reward is being offered in the case.

Anyone with information on the case is asked to call Crime Stoppers at (713) 222-TIPS, or the Houston Police Department Homicide Division at (713) 308-3600 or at (800) 887-5800.