BALTIMORE (WJZ)–Twelve people were sickened at Johns Hopkins at Keswick on Monday afternoon. They experienced similar symptoms to last week’s hazmat incident.

Hazmat crews were on the scene after 12 employees complained they were feeling ill.

Seven were taken to area hospitals. Five others refused treatment.

The employees appeared to have similar symptoms to that of more than 17 employees who were sickened last Tuesday at the office complex.

Those employees experienced dizziness, nausea, difficulty breathing and vomiting.

Area hospitals are being advised to report any illness fitting related criteria.

Baltimore health officials say the cause of last week’s problem was a hot water heater in the south building of the complex that was the source of nitrates and nitrites.

The investigation into the cause of Monday’s situation is still under investigation. The south building will be closed Tuesday to allow the investigation to continue. The north building will be open as usual.