SEATTLE -- Big, new developments on that botched clean-up of liquid mercury at Seattle City Light.

KIRO Team 7 Investigators first broke details of the secret spill earlier this week.

We found 23 city employees were exposed to poisonous levels of toxin. And we told how mercury was poured down the drain.

Now, Investigative Reporter Chris Halsne reveals how City Light may have violated our state's laws on dangerous waste.

Seattle City Light continues to sample the air inside its Bothell power plant for mercury vapors even though we found the initial spill occurred seven weeks ago.

Today, the state Department of Ecology sent an "immediate action" letter to City Light, demanding it locate and document some 20 pounds of unaccounted-for liquid mercury.

When an old pressure gauge, filled with 2 cups of mercury, exploded inside a substation Sept. 19, Seattle City Light workers broke every safety rule in the book. They cleaned up with squeegees and rags and without decontamination gear.

Records show they then poured the mercury-laden mop water down the sink, while water from a broken pipe carried globs of toxins down a second drain.

Nobody called the EPA or the state Department of Ecology, who both found out when Team 7 Investigators contacted them a month after the incident.

Ecology's Hazardous Waste compliance unit wants proof that all the mercury has been recovered. Spokesperson Larry Altose tells Investigative Reporter Chris Halsne, "We have concerns about things that we're seeing there and ways things were handled. Although Seattle City Light is telling us that they did clean out some traps in the pipes, J-traps in the pipes, we need to verify whether there has been contamination into the storm drain and into the septic system tank."

On top of the water quality issues, KIRO Team 7 Investigators have learned that a week after the spill, five barrels full of asbestos floor tile (also laced with mercury) was pulled from the substation.

Ecology wants to know if that has been properly disposed of. “These laws are designed to protect the public health and safety,” says Altose.

The Washington Department of Labor and Industries is also investigating some serious worker health violations. Internal memos and e-mail obtained by KIRO Team 7 Investigators show mercury was tracked off site, into cars, and possibly home to employees families.

Seattle City Light might have committed a federal crime by not reporting this spill to the EPA. That is currently under investigation.

In the meantime, City Light tells me, it has hired an outside clean-up specialist. Testing is under way on a storm water retention pond near the Bothell substation.