HOUSTON -

FBI agents on Wednesday investigated a suspicious package found at an elementary school.

Houston Independent School District officials said the envelope was sent to Franklin Elementary, 7171 Canal, and opened about 4 p.m. on Wednesday.

Most of the students had gone home for the day, but some were still there participating in an after-school program.

School district officials said preliminary testing showed that the envelope did not contain a dangerous substance.

This is the second time a suspicious envelope has been found at the school this academic year. Another one, containing a powdery substance, was found on Dec. 21. The substance was determined to be harmless.