Smash Mouth singer Steve Harwell was hospitalized Thursday, resulting in the cancellation of at least two concerts. The frontman experienced difficulty breathing at a sound check for Thursday night’s concert at the New Daisy Theater in Memphis, and decided to seek medical treatment, preempting the performance, according to TMZ.

The group’s Friday show at the Wildey Theatre in Edwardsville, Ill., was also affected. According to the Wildey’s Facebook page, the sold-out concert “has been postponed due to illness of lead singer Steve Harwell. We will have a new date once we schedule it with their management.”

Harwell, a founding Smash Mouth member since 1994, helped make famous songs such as “Star” and “I’m a Believer,” playing a large role in establishing the band’s signature retro sound.

It’s currently unclear if the band will be able to fulfill its performance obligations Saturday at the River Days Festival in Portsmouth, Ohio, or Sunday at the Elgin Festival Park in Elgin Park, Ill. Variety has reached out to the band’s manager for comment.

Two years ago, Harwell was diagnosed for cardiomyopathy, which impairs the heart’s ability to pump efficiently, and began taking medication for the condition. The performer has suffered other health mishaps, reportedly collapsing onstage at an August 2016 concert in Urbana, Ill., and leaving the showgrounds in an ambulance.

This year, Smash Mouth celebrates the 20th anniversary of the debut album “Fush Yu Mang,” released on July 8, 1997. The multi-platinum band received a Grammy nomination in 2000 for the song “All Star,” from their second album, “Astro Lounge.”