EL PASO, Texas -

An investigation continues after three teens, all students at Riverside High School, were reportedly found foaming at the mouth and having seizures in a parking lot.

All three students were hospitalized. One of them is in critical condition, according to the El Paso Fire Dept. The condition of the other two was not immediately known.

Ysleta Independent School District officials said in a statement that the students - two sophomores and one freshman - were off-campus for lunch when they were transported to a hospital after ingesting an unknown substance.

A source with EPFD tells ABC-7 that the  911 caller who dialed for help reported that the students may have been using a drug known as "spice".

Students we spoke with say that the parking lot is known to be a place where students smoke spice.

Spice is a synthetic form of marijuana illegal under Texas law. However, emergency crews have not given any confirmation that spice was used by the teenagers.