ZURICH A parliamentary investigation into the collapse of Credit Suisse will keep its files closed for 50 years, newspaper Aargauer Zeitung reported, triggering concerns among Swiss historians.

The investigating commission will hand over its files, which include witness statements and documents to the Swiss Federal Archives after a much longer gap than the usual 30 years, the paper said.

The Swiss parliament did not respond to a request for comment on Saturday.

The Swiss Society for History raised concerns about the length of time, with its president Sacha Zala writing to commission head, Isabelle Chassot, a law-maker from the Swiss upper house of parliament.

"Should researchers want to scientifically investigate the 2023 banking crisis, access to the CS files would be invaluable," Zala wrote, according to the newspaper.

"Ideally, it should be possible to secure and make accessible the archive after an appropriate protection period has expired and, if necessary, subject to historical research conditions," he added.

The investigation will focus on the activities of the Swiss government, financial regulator and central bank in the run up to emergency takeover of Credit Suisse by UBS in March.

The investigation is only the fifth of its kind in the country's modern history and the committee of lawmakers conducting it has sweeping powers to call on the Swiss cabinet, finance ministry and other state bodies.

The committee held its first regular meeting in Bern on Thursday, where it stressed the confidentiality of its proceedings.

It could have the power to question the Credit Suisse bankers involved, but they will not be the focus of the inquiry.

(Reporting by John Revill; editing by David Evans)