The Maui Police Department is investigating the vandalism of two large water storage tanks on Molokai, an incident that led to fears that hundreds of Hoolehua-area residents were exposed to contaminated drinking water and the closure of four schools on Wednesday.

But microbiological and chemical testing by the state Department of Health on Wednesday determined that the water is safe to resume normal usage and consumption, officials said.

The Department of Hawaiian Home Lands discovered the damage to both of their 3.5-million-gallon water storage tanks in Hoolehua on Tuesday, prompting warnings about the drinking water to some 1,800 customers.

Samples of the tank water were flown to a Health Department laboratory on Oahu on Tuesday night to expedite water-quality analysis.

DHHL spokeswoman Kuʻuwehi Hiraishi said the lid of one of the large tanks was completely torn off, while the lock on the second tank’s lid was broken. The tanks are nearly three stories high and dozens of feet in diameter.

The last time the tanks were seen undamaged was during a routine inspection Oct. 15, Hiraishi said.

“It’s very disappointing,” she said. “We don’t know why this happened or who did it.”

State Rep. Lynn DeCoite (D, Lanai-Molokai-Paia-Hana) called the incident “deeply troubling.”

“Water is our most precious resource,” DeCoite said in a statement. “This act of vandalism affects all of us doing the things we do in everyday life. It affects our families and disrupts our businesses, especially as we are all getting ready for the Thanksgiving holiday.

“Finding out what happened, getting a full report will hopefully help us make sure this does not happen in other communities across the state.”

Before the all-clear, officials were advising residents to seek alternative water sources for drinking, brushing teeth, washing hands, cooking, dishwashing and bathing.

DHHL was providing potable water from the fire hydrant next to the Kulana Oiwi conference room at 600 Maunaloa Highway for Hoolehua water system consumers, while the Maui County Board of Water Supply dispatched a water truck as an additional source.

Molokai High, Molokai Middle, Maunaloa Elementary and Kualapuu Public Conversion Charter schools were closed Wednesday due to the water problem, while Punana Leo o Molokai remained open because a previously scheduled field trip was being held, Hiraishi said.

Earlier in the year, the DHHL presented a draft environmental assessment that described a proposed $25 million in improvements to the Hoolehua water system, including upgrades to the water tanks.

According to the document, the two Hoolehua tanks have been in operation since 1934, and several of the valves, ladders and other secondary structures are rusted or not working.

In addition, the document calls for the construction of fencing around the tanks to increase security and restrict trespassing.