(Reuters) - The embattled warden of a Wisconsin prison that was under federal investigation was charged with misconduct in public office on Wednesday, court record showed, after four inmates at the maximum security facility died over the last year.

Randall Hepp, warden of the Waupun Correctional Institution in Waupun, was taken into custody by authorities in Dodge County one day after he announced his resignation, the local sheriff said at a briefing.

In March, the office of Governor Tony Evers said federal authorities were investigating prison staff who were suspected of being involved in a smuggling ring.

A series of inmate deaths have cast a shadow over the prison and how it has been run.

In June 2023, prisoner Dean Hoffman took his own life while in solitary confinement, prompting his daughter to file a federal lawsuit in February accusing prison officials of failing to provide him with care and medication for his mental health.

Two other inmates died in October. Tyshun Lemons suffered a fentanyl overdose while Cameron Williams died of a stroke, according to the Milwaukee Journal Sentinel.

In February, Donald Maier was found dead at the prison. The cause of his death has yet to be made public.

The prison, home to 1,000 inmates about 70 miles (113 km)northwest of Milwaukee, has been on lockdown since March 2023 due to staff shortages. A group of inmates filed a federal lawsuit in Milwaukee, saying the lockdown amounts to cruel and unusual punishment.

(Reporting by Brendan O'Brien in Chicago; Editing by Daniel Wallis)