Two sisters tried to smuggle explosives into Israel from Gaza using tubes labeled for medication, taking advantage of an entry permit issued for one of them to seek cancer treatment, Israeli officials said Wednesday.

The Shin Bet security service, which said it foiled the smuggling attempt at the Erez Crossing earlier in the day, accused the two of aiding terror activity at the behest of the Hamas terror group.

The explosives were “sent by Hamas and it is believed that they were meant to be used to carry out attacks in Israel in the near future,” the Shin Bet said in a statement.

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According to the security agency, the explosives were hidden inside tubes labeled “medical materials.” It said the materials were to be used to manufacture improvised explosive devices.

The sisters, both residents of Gaza, received permits to enter Israel as one of them suffers from cancer and was traveling to an Israeli hospital for treatment.

The explosives were found during a security check and were disposed of by police sappers, the Shin Bet said. The two women were detained for questioning by the Shin Bet. They were not named.

“Unfortunately, this is more proof that terror groups in Gaza are continuing to take advantage of humanitarian channels to export terror into Israel’s heartland,” Defense Ministry Crossing Points Authority head Kamil Abu Rokan said in a statement. “The security checks at the crossing worked exactly as we expect and with notable professionalism.”

Prime Minister Benjamin Netanyahu alluded to the sisters’ case earlier in the day during a Knesset committee hearing.

Though he did not refer to the specifics of the case, as it had yet to be announced by the Shin Bet, the prime minister mentioned Hamas’s attempts to smuggle explosives with sick Gazans who have permits to visit Israeli hospitals.

According to Netanyahu, cases like this one are why Palestinians in Gaza will not likely be able to work inside Israel, as some other politicians have suggested.

While Israel tightly controls its crossings in and out of Gaza as part of a security blockade, it allows tens of thousands of Palestinians to leave the Strip to seek medical treatment in Israel, the West Bank and Jordan each year.

Last month Deputy Defense Minister Eli Ben Dahan claimed that Hamas was using Gazan cancer victims as mules to smuggle money and gold into Israel to finance terror operations.

The claim came in response to a report which found a sharp drop in the number of cancer patients given permits to cross into Israel.