ROMEO, Mich. -- New tests show Michigan's Washington Elementary School in the Romeo School District to be free of black mold. Meanwhile, a cleaning and storage firm has filed a $1.5 million lawsuit against the district.

District officials began allowing students to return Jan. 18, and slated another round of tests for this week. District officials said they believe tests will show the school is safe to open. Washington Elementary has been shut since the beginning of the school year, forcing its 500 students to attend other district schools because of health concerns. Black mold can cause severe breathing problems.

District officials have withheld payment to at least three companies they believe misled them, performed unauthorized repairs or did shoddy work. The companies have threatened to sue. The district has spent more than $100,000 in the past few months on legal fees related to the cleanup.

Kalamazoo-based Wonder Makers Environmental Inc., which told the school district in the summer it found evidence of the mold throughout the school, denies it did anything wrong.

Statewide Disaster Restoration Inc. was hired by the school district to remove, clean and store furniture after black mold was found in the district's Washington Elementary School. The district approved $200,000 for the work, and says it was charged more than $700,000 in unauthorized charges. The cleaning and storage firm has filed a $1.5 million lawsuit against the district.

To date, the school district has spent more than $1 million to clean the school, even as school officials question how severe the problem really was. The final bill with legal fees could total over $2 million.

Several potentially hazardous forms of mold were found at the school last May. The building was ordered closed until it was cleaned of mold. Other schools throughout Macomb County hosted the students from Washington Elementary while that school was closed. Most students were able to return to the school last week.

Crews this week began cleaning portions of the school with bleach water and bacteria-killing vacuum cleaners. The cleanup this week is less extensive than ones called for this summer by Wonder Makers. Those cleanup measures included major roof renovations, sending crews inside the building wearing NASA-style bubble suits and replacing carpeting.