Classes will start Thursday at Crossroads Elementary Science and Montessori in St. Paul as planned, after a delay caused by the concern that toxic vapors under the building’s foundation could have leaked into the building.

Test results from the Minnesota Pollution Control Agency showed no dangerous chemicals in the air at the school at 543 Front Av., but school officials have taken additional steps to make sure it stays safe, St. Paul Public Schools said Tuesday.

A ventilation system has been installed that takes soil vapor from under the foundation and vents it outside. The school also will do follow-up air-quality testing.

The start of school at Crossroads was pushed from Tuesday to Thursday for grades 1 through 5. Pre-K and kindergarten hadn’t been scheduled to start until Thursday.

A meeting for parents of Crossroads students will be held from 6 to 7 p.m. Thursday to talk about the new ventilation system, air testing and health information.