Comerica Bank & Trust, the company appointed to manage Prince's enormous assets, took off the gloves this week to fight his heirs' accusations that it has mishandled the estate.

Since Prince's death in April 2016, his six heirs have challenged many steps that Comerica and its predecessor took as special administrators of the estate, which is valued at between $100 million and $300 million before taxes. Prince, 57, died without a will.

In the most detailed documents about the musician's estate to date, Comerica asserted it has made painstaking efforts to protect his music and other intellectual property. The bank estimated it already has prevented the illegal sale of more than $50 million in music, videos, T-shirts and other Prince merchandise.

Sharon Nelson, John Nelson and Norrine Nelson — three of Prince's five half-siblings — filed a petition in October to remove Comerica as special administrator.

Prince's sister, Tyka Nelson, and half-siblings Omarr Baker and Alfred Jackson, are his other heirs. Baker filed a petition last week supporting Comerica. The other two heirs have yet to weigh in.

Comerica's attorneys said in filings with the Carver County District Court last week that Prince's disgruntled heirs relied on vague accusations that the bank's employees are not competent to administer the estate and that two trust officers were "aggressive, temperamental, rude, and condescending."

Comerica said that it will continue to work to improve its relationship with all of the heirs, "but building (or repairing) a relationship requires engagement from all parties and, to date, the personal representative has not had willing partners in the Nelsons," the bank's attorneys said. Comerica claims that the complaining siblings did not attend several meetings.

Comerica hired the trust officer who administered the estate of Elvis Presley.

They also hired MarkMonitor to provide monitoring and enforcement services related to Prince's assets. More than half of Fortune 100 companies use MarkMonitor to protect their brands, the bank said.

MarkMonitor filed a report with the court saying it has reviewed tens of thousands of listings on such online sales sites as eBay, Amazon, Etsy and iOffer since April, and got 8,660 listings removed and 584 links shut down across 158 websites.

About 37 percent of all Prince T-shirts have been removed from Amazon U.S., the report said.

In the petition to replace Comerica, the Nelsons objected to the bank's removal of unreleased music and videos from a vault at Paisley Park Studio in Chanhassen. The materials were trucked to a facility in Los Angeles.

Comerica said it did so because mold and water had damaged some of the materials.

Comerica denied accusations that it had moved the items without informing the heirs.

"Unfortunately, rather than attempting to work cooperatively with the personal representative to address any concerns, the Nelsons have resorted to filing a petition replete with objectively false statements and baseless personal attacks in a misguided attempt to remove the personal representative," the bank's attorneys wrote.

"The Nelsons are certainly entitled to their own opinions, but they are not entitled to their own facts."