With the boil notice finally lifted, Houston Mayor Sylvester Turner is still searching for answers.

"Stuff happens, whether I like it or don't like it," Mayor Sylvester Turner tells CultureMap news partner ABC13. According to Turner, a transformer at the water plant failed, as well as the backup transformer. Generators never kicked in.

The city has a long-standing $56 million contract with NRG Energy Services to have backup power generation equipment at the East Water Purification Plant.

"Well, we did have generators, but when the transformers failed to operate, it prevented the generators from being connected in order to provide the additional power," Turner adds. NRG told ABC13 Investigates the problem was with the two city-owned transformers and was not on its end.

"We do know that the two transformers malfunctioned. One was a backup to the other. It was just one of those unique circumstances in which you have these transformers that malfunction and then you have the backup that malfunctioned," Turner says.

When asked by ABC13 how this could have happened, the City of Houston staff have few answers.

"(We're) working through the issues to understand exactly what the failure was to make sure we have every step in place that we make sure this doesn't happen again," Carol Haddock, the Houston Public Works director, tells ABC13.

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Continue reading this story, with accompanying video, on our news partner ABC13.

With the issues surrounding the city-wide boil notice still unresolved, Houston Independent School District has announced all its campuses and facilities will be closed on Tuesday, November 29. This comes after classes were canceled on Monday, November 28.

"This decision has been made due to the logistical challenges caused by the notice," district staff notes in an email. "Those challenges prevent the district from being able to provide meals for its students and ensure safe water is available for students and staff."

The email goes on to add that all HISD employees will be working remotely unless otherwise instructed by the chief of their business area.

While most kids will no doubt enjoy yet another day off, HISD encourages students to "engage with digital academic resources that are available 24/7 online.

This closure announcement comes as other districts and colleges closed campuses on Monday. As CultureMap previously reported, the city was put on a boil notice after water pressure dropped below the City of Houston's required minimum of 20 PSI due to a power outage at the East Water Purification Plan around 10:30 am Sunday, November 27.

Under city guidelines and those set in part by the Texas Commission on Environmental Quality, city water pressure must be at least 20 DPI to ensure contaminants do not enter the flow. Notably, according to the director of Houston Water, Yvonne Williams Forrest, the city's water pressure never dropped to zero — but did fall below the regulatory limit.

Additionally, Forrest says the city boil notice could last until the early hours of Tuesday, November 29.

As reported by CultureMap news partner ABC13, Houston Mayor Sylvester Turner provided a timeline for the outage on Sunday:

• 10:30 am: East water purification plants 1 and 2 lose power

• Plant 3 loses power, 14 sensors below 20 PSI for less than 2 minutes, 2 sensors below 20 PSI for 30 minutes, 5 sensors never fell below 20 PSI

• 12:15 pm: Power restored to plants 1 and 2

• 12:30 pm: Power restored to plant 3

• 3:30 pm: All sensors back to 35 PSI

Residents expressed outrage on social media that they weren't notified of the boil notice until late Sunday night. In response that same night, several school districts — including Houston ISD — announced they would close on Monday, November 28. Parents should watch their school districts' social media for updates regarding classes resuming.

Concerned residents who are unsure if the boil notice affects their neighborhood can view this map that displays the entire affected.

Early Monday, the City of Houston announced on Twitter that the aforementioned Texas Commission on Environmental Quality (TCEQ) approved a plan by the Houston Public Works department to sample water and send to labs for testing.

Boil notices are nothing new to the Gulf Coast and Greater Houston areas, given the propensity for storms and flooding. But as longtime Houstonians know, there are few key things to remember when under a boil notice. These tips include:

Avoiding ice from an automated ice machines

The City of Houston also reminds residents to call 3-1-1 for any boil-notice-related questions.