(Reuters) - Lawyers for Elliott Broidy, a top fundraiser for U.S. President Donald Trump, have sent out more than 40 subpoenas to internet service providers, lobbying firms and others in an escalating legal fight against Qatar for allegedly hacking into his emails, two people with knowledge of the matter said.

The subpoenas, issued in recent weeks as part of a civil suit filed by Broidy in a Los Angeles federal court in March, come as Qatar and its rivals wage a multi-million dollar battle for influence in Washington over the Trump administration’s policies toward the Gulf region.

The lawsuit accuses Qatar of orchestrating the theft and leaking of Broidy’s emails as retribution for his support of the United Arab Emirates and Saudi Arabia, which along with Egypt and Bahrain levied economic sanctions against Qatar last June.

The emails were distributed to various media outlets, leading to weeks of damaging stories about Broidy.

Nicolas Muzin and his lobbying firm Stonington Strategies LLC are also named as defendants in the case. Both Qatar and Muzin have denied involvement in any hacking.

Broidy is scheduled to file an amended complaint on Thursday to the Los Angeles federal court. His lawyers will expand the list of defendants, adding people suspected of carrying out the hack or disseminating material, a third person with knowledge of the matter said.

One subpoena seen by Reuters asked the recipient to hand over documentation of any communications related to Broidy with more than a dozen lobbying and public relation firms, some of which are registered as foreign agents for Qatar.

Another recipient of a subpoena was Avenue Strategies Global LLC, a lobbying firm founded by former Trump campaign manager Corey Lewandowski and Barry Bennett, according to two sources with knowledge of the subpoena.

Lewandowski had left Avenue Strategies by the time it was hired by the Qatari embassy as a client. Bennett, who was an adviser to the Trump campaign, did not respond to a request for comment.

It was not clear whether the subpoenas would prove effective. One source said he believed most of the lobbying firms would at least initially decline to provide information and contest the matter in court.