Police say they are investigating allegations of a secret price-fixing arrangement by companies who organise the trips for students.
Investigators have raided the homes of executives and frozen bank accounts.
At least six travel agencies are accused of violating competition rules.
They are suspected of colluding on prices before responding to an education ministry tender to take students to Holocaust memorials.
When the Israeli education ministry approached a number of different companies, it received identical quotes.
Reports say the alleged collusion was aimed at artificially inflating prices.
Drone video shows the Auschwitz-Birkenau concentration camp
Why did ordinary people commit atrocities in the Holocaust?
The Holocaust year by year
Thousands of Israeli high school students travel to memorials at World War Two death camps every year. A trip can cost several thousand shekels per student (1,000 shekels is worth Â£177), according to reports in Israeli media.
The BBC's Kevin Connolly, in Jerusalem, says that for many Israeli high school students a visit to the site of the Nazi death camps in southern Poland is a rite of passage, which gives them a direct sense of connection to the Holocaust - the defining tragedy of modern Jewish history.
If the allegations are proved to be true, our correspondent adds, there will be shock in Israel that a form of tourism that is viewed with great solemnity may have been the subject of illegal business practices.
Some six million Jews were murdered by the Nazis during the Holocaust, mainly in death camps in occupied Poland. More than a million people, mostly Jews, were killed in Auschwitz alone.

Homes have been added to My NHS, part the NHS Choices site, allowing users to leave ratings and reviews to help other people assess services.
Each care home is scored on its level of safety, staff turnover and food hygiene, among other standards.
The National Care Association said if information was not up to date, it could be "unfair" to care providers.
On the website, a database can be searched using a postcode, region or home name to check on facilities with or without nursing.
People can access:
Health Minister Alistair Burt said:  "We know how difficult important decisions about care for a loved one can be - this is a victory for those who are worried about care - with a click of a button the public will be able to make an informed choice about care and make those difficult decisions easier.
"This data will show clearly the difference in quality across care homes and will help drive up standards by highlighting poor performers which will mean they have to shape up their services or lose out."
Nadra Ahmed, chair of the National Care Association, which represents independent care sector providers, said the move could help people "answer some of the questions" they may have about care.
But she warned that if the "snapshot" of the provider's rating or profile on the site was not regularly updated it could disadvantage those who improve their service.
"I don't know how [improvements] would be indicated... especially if that report is not going to be reviewed for a period of time, which would be unfair."
She added: "Nothing beats actually going to see a service for yourself. If you think that it's good [but the website] says there's something that's not quite right, don't let it put you off.
"When you look at the website you know that responsible services who may have an inadequate rating will be working towards making that better."
Nine executives at Israeli travel agencies have been arrested on suspicion of fixing the price of high school students' trips to former Nazi death camps, including Auschwitz.
[NEXT_CONCEPT]
The performance of every care home in England can now be compared on an NHS website.