Nassau County has halted work on its $12 million contract with an environmental company at the center of a corruption case against state Sen. Dean Skelos and his son.

Public works officials Tuesday sent a letter to Arizona-based AbTech Industries to notify the firm that it was suspending all work, effective immediately, under the 2013 contract to design and install technology to filter pollutants from storm-water drainpipes.

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"No additional work is to be performed on the contract until such time, if at all, the county notifies AbTech in writing that the county has lifted" the suspension, Public Works Commissioner Shila Shah-Gavnoudias wrote to AbTech CEO Glenn R. Rink.

ColumnJanison: Feds' Skelos charges outline multi-sided scandalSee alsoRead the complaint vs. SkelosMore coverageSenate Majority Leader Dean Skelos, Adam Skelos face corruption charges

The suspension comes about a week after federal prosecutors charged Skelos (R-Rockville Centre) and his son, Adam, with conspiracy, bribery and extortion. They allege that Dean Skelos, who resigned Monday as Senate majority leader, pressured a large real estate developer with an interest in state legislation to pay Adam Skelos through companies including AbTech. Dean and Adam Skelos say they are not guilty.

Shah-Gavnoudias' letter gave no justification for the suspension, but a source has said it was tied to the "cloud hanging over the project."

AbTech spokeswoman Lisa Linden said that the firm was "deeply disappointed" by the decision, "given Nassau County's need for the services we provide, and our unparalleled ability to provide them."

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AbTech paid Adam Skelos $198,000 over three years to help the company win government contracts, according to prosecutors. To date, the county has paid AbTech only $150,141 for initial design and study work, and pending claims total another $8,916.