Pilots were up in arms on Monday over what they called "delays" in the Israel Air Force's handling of the crisis that erupted in the elite military branch over the weekend with the discovery of carcinogenic material in one of Israel's most advanced F-16I fighter jets. Col. Erez Barnboim, the IAF's chief medical officer, said Monday that it was likely there were pilots who were exposed to formaldehyde in high concentration. IDF sources said that hundreds of pilots have flown the F-16I in recent years and might have been exposed to the carcinogenic material. "Formaldehyde can cause cancer and as doctors we are therefore obligated to update people that may have been exposed to it," Barnboim said. "We so far do not know of anyone who is sick, but we will continue to closely watch them (pilots and technical personnel) and we won't stop until we are sure that everyone is fine." On Friday, IAF chief Maj.-Gen. Elazar Shkedy decided to ground all F-16I training flights after formaldehyde was found in the cockpit of one of the aircraft. Shkedy made the decision to suspend training flights - the plane will continue to be used in necessary operations - after a number of pilots complained of a bad smell coming from the cockpit of one of the planes. The IDF Medical Branch conducted tests and discovered that the smell was caused by a type of formaldehyde known to be carcinogenic in high concentration. On Sunday night, Shkedy met with the all of the IAF's F-16I pilots and pledged that the IDF would do everything possible to discover the cause of the flaw. "I take this very seriously and we will not spare any resources to understand the issue and treat it appropriately in the short and long term," Shkedy said. A senior officer who attended the meeting said Monday that the pilots were "deeply disturbed" by what they heard from Shkedy and asked "difficult and probing" questions. "It was a difficult meeting that did not go over as well as planned," the officer said. A team of IAF technical personnel, their American counterparts and the plane's manufacturer - Lockheed Martin - has been set up to investigate the incident. Sources indicated Monday that the source of the formaldehyde was likely the F-16I air conditioning system, since the carcinogenic material is a known by-product of jet engine exhaust. While the incident appears to be isolated to one plane, Shkedy's decision to ground F-16I training flights has raised eyebrows around the world. Soke 4,000 F-16s have been manufactured since production in the US began in 1976 and it is considered one of the most-sold fighter jets in existence today. The variant that Israel has, called the F-16I, is also in operation in Singapore, Poland, Greece and the US. Israel has been receiving about two planes a month since 2004 and is expected to receive the complete 102 it has ordered by the end of the year. Defense officials said Monday that Shkedy's decision to ground the training flights was indicative of just how severe the case was and how concerned the IAF is that its pilots may have been exposed to a high concentration of carcinogenic material. "This is the most advanced fighter jet in Israel's arsenal today and when there is a problem with it, people take interest," a defense official said on Monday. From an operational perspective, the decision to ground the training flights does not immediately affect the IAF, which continues to use the jets for operations, mainly in the Gaza Strip. "Pilots are familiar with the plane and a short break will not change that," the official said.