R.A. Brown Middle School and Ladd Acres Elementary School in Hillsboro were on lockout Tuesday morning after five explosive devices - the equivalent of what a police official called a science class experiment -- were found in a skate park near the schools.

Students were in classes when a Hillsboro parks employee found the first of the five plastic bottles containing a corrosive liquid at 9:25 a.m., officials said.

The top of that bottle popped and the incident was initially reported as an "explosion," Hillsboro Police spokesperson Lt. Henry Reimann said, adding that neither the parks employee nor anyone else was injured.

Reimann said the five plastic bottles were found in a variety of locations at the Reedville Skate Park at Southeast Frances Street and Cornelius Pass Road.

The design of the devices as well as their location -- the middle school is at 1505 S.W. Cornelius Pass Road; the elementary school at 2425 S.W. Cornelius Pass Road - have led authorities to speculate that a student may have been involved in the devices' construction. He said the investigation continues.

The lockout was lifted at 10 a.m., Hillsboro schools spokesperson Beth Graser said.

Graser said a notice was read to Brown middle school students at the beginning of their third period telling them to not pick up strange objects. Also, the notice encourged them to share information with authorities that is related to the morning incident.

Graser emphasized, however, that it's not known at this time who was responsible for placing the five bottles at the park, be it young person or adult.

-- Allan Brettman