The Dallas County district attorney's office is investigating efforts by the Cedar Hill mayor and other officials to pump millions of tax dollars into the deteriorating downtown where they and their families own property.

This week, a grand jury subpoenaed numerous City Hall records tied to a special tax zone approved by Mayor Rob Franke and other City Council members in 2016, according to sources with knowledge of the matter.

The probe was triggered by a Dallas Morning News investigation that found Franke, other officials and their families owned at least 25 properties in the zone, putting themselves in position to profit. But they did not tell the public.

Texas’ conflict-of-interest law bars public officials from voting or participating in certain matters involving their businesses or real property.

Franke and other city officials did not respond to requests for comment about the investigation. They previously told The News they had followed state law and that the tax zone is intended to benefit the entire city.

A spokeswoman for the district attorney's office declined to comment, saying the office does not discuss investigations.

A member of a citizen watchdog group that has been monitoring City Council meetings over the last two years applauded the probe.

"This is an issue of integrity for our local government, and we need to make sure the integrity of our leadership is maintained,’’ said Katie Myers, a Cedar Hill resident and retired medical doctor.

Legal experts who reviewed the special tax zone vote as well as other council actions for The News described them as clear conflicts of interest.

Former council member Chris Parvin's family owns 30 acres of farmland and several other properties downtown, including his White Rhino Coffee Shop, The News reported. Franke has owned at least nine properties in the zone, valued at close to $1 million.

Council member Jami McCain and her husband lead a church that owns one downtown property. And Chad McCurdy, a former planning and zoning commissioner, has owned five properties through his business, The News found.

McCurdy is now a member of the City Council, having replaced Parvin in May after he did not seek re-election.

Six residents disturbed by what they call their town officials' conflicts of interest have been closely monitoring town business. From left: Tom Myers, Terri Sengbush, Katie Myers, Wes Pool, M.G. Johnson and Larry Sengbush. (File Photo / Staff)

Parvin made the motion to approve the tax zone in December 2016. It passed unanimously. Mayor Franke was not present but signed the ordinance that made it official.

The zone, designed to pay for street, water and sewer improvements, has been projected to generate $160 million in new development and boost property values.

The town's ethics policy required council members to disclose all their property holdings. The mayor and other members, however, failed to comply after 2008, The News found. The month after council members approved the tax zone, they got rid of the disclosure requirement without any public discussion.

The mayor told The News last year that he should have disclosed his properties under the former policy, calling the mistake "embarrassing.''

In an interview, he blamed city administrators for failing to remind him.

“Sorry to throw you under the bus, guys,’’ Franke said.