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HIALEAH (CBSMiami) – Hialeah’s water may not be safe to drink after testing positive for E. coli bacteria last Thursday.

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The water needs two days of tests, by two private labs, to come back clean for a boil water advisory to be lifted.

So what caused the contamination?  The city’s website makes vague reference to a possible construction accident, and says the water warning continues “until further notice.”

Not everyone has noticed.  At a popular restaurant on West 49th Street, patrons were drinking water in glasses being filled straight from the tap.

“We’re not affected,” the manager told a CBS4 News crew.  “It came out on the news, but we’re not affected.”

But he is affected.  The restaurant is in the middle of a boil water area that encompasses some 1,500-square blocks, a huge chunk of the city.

Many business owners are aware of and abiding by the water warning.

“We can’t even make coffee, because it requires the water to be boiled and the coffee machine doesn’t boil the water,” said Miguel Cedron-Ron, owner of the Palm Springs Mile Valero service station and cafeteria.

And many homeowners are being careful.

Betty Aguilar said she has been boiling tap water and putting it in jugs in the refrigerator for cooking, drinking and brushing their teeth.

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“We bought some bottled water, also, from the store,” added Betty’s father, Jorge Campos.

Rodney Herrera was washing his boat with the garden hose, but his refrigerator was stocked with spring water.

“I saw the news, the story about the contaminated water,” Herrera said.  “I’m using bottled water all the time.”

Why has the water warning dragged into a sixth day?

Mayor Carlos Hernandez was nowhere to be found, but his Chief of Staff, Arnie Alonso, told CBS4, “We believe the cause may be county sewer pump stations that overflowed during the recent heavy rains.”

A spokesperson for Miami-Dade county public works said that’s nonsense.

“There is no accuracy whatsoever to the notion that sewer pump stations somehow contaminated the water system,” said Miami-Dade’s Jennifer Messimer.  “They are completely separate, closed systems.”

In fact, CBS4 News has learned that Miami-Dade Mayor Carlos Gimenez personally met with officials in Hialeah Tuesday afternoon, reasserting that the contamination issue is somewhere in Hialeah’s system, and in no way connected to county water and sewer operations.

The county supplies Hialeah with water that tests clean. The problem Miami-Dade says is somewhere in the city’s distribution pipes. The best guess:  A construction accident of some sort that caused a drop in pressure, letting contaminated ground water into a pipe.

Hialeah hopes to test clean, by both testing companies, for a second day tomorrow – and lift the warning by late afternoon.

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CLICK HERE to view a map of the area encompassing the boil warning.