SAN DIEGO -- San Diego police are investigating whether three Metropolitan Transit System bus drivers were under the influence of marijuana-laced brownies during their routes, officials say.

Metropolitan Transit System spokesmanRob Schupp said three drivers became sickened and reported feeling “dizzy” Sunday while on their routes, possibly after eating pot-laced brownies handed out by another employee.

Previous reports incorrectly said four drivers were sickened.

Transit officials say the three bus drivers acted appropriately by pulling off the road once they realized they had become ill. Replacement drivers were called in, according to NBCSanDiego.com.

It was not known if passengers were on board, or for how long the bus operators were driving while feeling ill, according to NBCSanDiego.com.

View NBCSanDiego.com's story on the bus investigation

According to transit system officials, drug tests were administered to the employees who reported feeling sick. The allegation of the drivers eating the drug-laced brownies, however, has not been confirmed by San Diego police, according to NBCSanDiego.com.

All three, plus an additional employee who allegedly distributed the suspected baked goods, were placed on paid leave while authorities conduct an internal investigation.

Metro Transportation System chief Paul Jablonski says the drivers followed procedures to the letter and supervisors acted quickly to protect the public, according to The Associated Press.

Metro officials say they have a comprehensive drug and alcohol policy that tests all new employees and conducts random tests throughout the year. The program exceeds guidelines set forth by the Department of Transportation, according to NBCLosAngeles.

NBCSanDiego.com's Lauren Steussy and Monica Garske contributed to this story.

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