Taylor Swift's Austria concerts canceled after suspected terror plot was foiled

Authorities in Austria discovered a potential terror plot targeting a concert venue. A 19-year-old suspect, believed to have pledged allegiance to ISIS, was arrested. Chemical substances were found at the suspect's home, which are being analyzed for potential use in explosives. A second suspect has also been detained. As a precaution, concert organizers canceled the shows and announced ticket refunds to ensure public safety.

What did the authorities discover that led to the arrest of the suspects?

What group did the 19-year-old suspect allegedly pledge an oath to?

What substances were found at the suspect's home?

What is the status of the second suspect mentioned in the text?

What action did concert organizers take in response to the situation?