TEL AVIV (JTA) — Nine suspects were arrested in what Israeli police believe is a criminal ring that monopolized the market for school trips to Poland in an effort to fix prices.

Among those arrested following police raids Monday morning on homes and offices were a high-level staffer of a large travel agency and two CEOs of smaller agencies, according to police spokeswoman Luba Samri. Israel’s antitrust authority also included searches of bank accounts in its investigation.

The suspects are accused of violating antitrust laws, accepting bribes and committing fraud.

The antitrust authority alleges that officials in the top travel agencies teamed to fix prices for groups of young Israelis traveling to Poland for Jewish seminars and heritage trips. According to Israeli media reports, the suspects won the tender from Israel’s Ministry of Education to coordinate and facilitate school trips to Poland.

Organized school trips to Poland are commonplace for young Israeli students. They typically cost parents thousands of shekels, making them inaccessible to lower-income students.