A middle school was locked down for three hours Thursday morning as SWAT teams searched the campus for a man who reportedly was brandishing a knife, police said.

"A student reported she was approached by a man in all black armed with a knife," said Officer Trish Hoffman of the Albuquerque Police Department.

"We've conducted a number of searches inside the school and secondary searches outside the school, and we haven't located anybody," she said.

Police also were looking at videotape of the outside of James Monroe Middle School, she said.

The girl reported that the man was "outside the school near a portable or by the bathroom or something like that," Hoffman said.

"We don't know if he touched her," Hoffman said.

The school was locked down at 8:55 a.m. and was reopened at 11:50 a.m., said Rigo Chavez, Albuquerque Public Schools spokesman.

Two elementary schools — one about three-quarters of a mile to the northwest and the other about a mile to the west — were locked down as a precaution, he said.

Those two schools were reopened shortly before 11 a.m., Hoffman said.

Chavez said he did not immediately know how many people were involved in the lockdowns.

An Albuquerque police SWAT team — along with SWAT teams from the school district, Bernalillo County Sheriff's Department and Rio Rancho Department of Public Safety — responded to the middle school, Hoffman said.