(Reuters) - Pennsylvania environmental regulators on Monday issued another notice of violation to Energy Transfer Partners LP’s Sunoco Mariner East 2 natural gas liquids pipeline for releasing drilling fluids into a wetland.

The company told the Pennsylvania Department of Environmental Protection (DEP) it released less than one gallon (4 liters) of drilling fluids - usually a mix of clay and water - into a wetland in Shirley Township in Huntingdon County located about 80 miles (129 kilometers) west of Harrisburg, the state capital. The spill was associated with a horizontal drill.

The DEP said it must approve before ETP can resume drilling at the site.

This is the latest in a long series of spills by the $2.5 billion project that have slowed its construction.

Since May 2017, the DEP said the project had 108 inadvertent releases, or spills, prompting the environmental regulator to issue 46 notices of violation.

Officials at ETP were not immediately available for comment.

It was ETP’s second release into this wetland after spilling between 5,000-10,000 gallons in the area in October. The DEP issued a notice of violation for that earlier spill.

The latest release comes after Pennsylvania utility regulators on March 7 suspended operations of ETP’s Sunoco Mariner East 1 liquids pipeline after sinkholes were discovered near the project.

The shutdown of Mariner 1 and delays for Mariner 2 have forced shippers, including Range Resources Corp, to find another home for their liquids and is likely causing more ethane to be rejected into the region’s natural gas pipelines, according to analysts.

Mariner 1 transports up to 70,000 barrels per day (bpd) of propane and ethane from the Marcellus and Utica shale formations in western Pennsylvania to customers in the state and elsewhere, including ETP’s Marcus Hook industrial complex near Philadelphia.

The sinkholes were near the area where construction is under way for Mariner 2. The order stopping flows on Mariner 1 did not affect work on Mariner 2.

Construction of Mariner 2, which started in early 2017, was originally expected to be completed in the third quarter of 2017 but has been delayed by repeated work stoppages by Pennsylvania regulators, among other things.

ETP has said it expects to complete Mariner 2 by the end of the second quarter.

Once complete, Mariner 2 will expand the total capacity of the Mariner East project to 345,000 bpd and open the pipe to suppliers in Ohio and West Virginia.