HOUSTON -

What started as a routine trip to school for a 4-year-old Houston ISD student ended in a way no one would have ever imagined.

The 4-year-old boy was left alone in the private van that picked him up and was supposed to drop him off at Fonwood Early Childhood Center in northeast Houston.

For nearly two hours, no one knew where the boy was. The driver, 32-year-old Miriam Contreras, has since been charged with child endangerment.

The boy's mother claims Contreras wasn't paying attention when she dropped the kids off at school Tuesday morning. She says Contreras failed to realize that her son had fallen asleep in the van.

After the school discovered he was absent, campus administrators immediately called his parents and police.

A source told Local 2 police tracked down Contreras to a nearby Zumba exercise studio near the 9000 block of East Mt. Houston. The van was parked in the lot.

"Anthony was on the bus. They went to go knock on the window. He knocked back and they located her inside," said Crystal Ortiz.

HISD police arrested Contreras. The 4-year-old wasn't hurt and was reunited with his family.

"She didn't intentionally mean to put my child in harm's way. What she did was very negligent. She should be checking the bus every day. We entrust our kids to these people," said Crystal Ortiz.

An HISD spokesperson told Local 2 Garcia Bus Company operates the van and that HISD does not contract with the company for bus service, that it's a private service that parents contract with.

As a result of Tuesday's incident, HISD says school officials will conduct a thorough review of this company's policies and procedures and try to determine what action, if any, will be taken.