A boil water order in Oak Bluffs was extended late Tuesday evening after test results from town water samples came back from the state Department of Environmental Protection.

Two out of five water samples tested positive for fecal indicator bacteria, interim water superintendent Paul Provost said. The DEP is slated to send a representative to the Island Wednesday morning to meet with town and water district officials. The main source of the problem is the Lagoon Pond well.

Mr. Provost said town officials and the DEP will decide whether to chlorinate the water or shut down the well altogether. The well is unlikely to be shut down, Mr. Provost said. Most towns chlorinate their water regularly, but Oak Bluffs does not disinfect town water. Escherichia coli, or e. coli, was not found to be present, the water superintendent said.

The boil water order was issued by the DEP Monday, prompting a run on bottled water on local stores by residents. The town handed out free bottled water as well. Public health officials said residents on the town water system should boil water used for cooking, drinking and tooth brushing. Showering is fine. Indicator bacteria can pose a health threat to the elderly and people with compromised immune systems.

The Martha's Vineyard Hospital invoked a protocol Monday for using an alternate water source for staff and patients.

The testing was expected to take 48 hours but a new accelerated testing method that shortens the incubation period to 24 hours was used, Mr. Provost told the Gazette late Tuesday. Rhode Island Analytics, the company that performs the testing, had been lobbying the DEP to accept the new testing methods.