The law firm hired by Gov. Christie's office to investigate the George Washington Bridge lane closure scandal has billed the state more than $8 million.

The latest invoices, released late Friday by the state attorney general's office, showed that Gibson Dunn & Crutcher LLP billed the state more than $200,000 between May and August.

The firm released a report in March 2014 that said Christie had no involvement in the lane closures, which federal prosecutors allege were carried out by three former allies of Christie's to punish a mayor who didn't endorse the governor's reelection.

More recently, Gibson Dunn has been fighting efforts by attorneys for two of those former allies facing federal criminal charges. They want the firm to turn over notes from the interviews it conducted to produce the report, though Gibson Dunn has said some of the records don't exist.

The invoices released Friday - all with the heading "Subpoena Response/Internal Investigation" - show continued work on the case by a lawyer who is cohosting a fund-raiser for Christie's presidential campaign next week in Los Angeles. The lawyer, Debra Wong Yang, was billing hours through the end of August, according to invoices.

- Maddie Hanna