The Czech Foreign Ministry expressed concern Thursday over the discovery of a large, illegal weapons stockpile at the home of the Palestinian ambassador in Prague, Jamel al-Jamal, a day after he was killed in an explosion there.

A ministry statement said that the findings possibly constitute a breach of diplomatic rules, and warrant a clarification from Palestinian officials, Reuters reported.

“In such case, the Vienna Convention on diplomatic relations may have been breached and we will demand an explanation,” the ministry said in a statement.

Respekt, a Czech weekly newspaper, reported that the discovered arsenal was enough to arm a unit of 10 men.

Czech police spokeswoman Andrea Zoulova confirmed that arms had been found in the ambassador’s residence, which is located within a newly constructed Palestinian diplomatic mission in the city.

The stockpile included heavy firearms being held illegally, unbeknownst to Czech authorities, according to a Channel 2 news report.

Reuters quoted an unnamed Palestinian official claiming that the mission’s staff had submitted the weapons to Czech authorities. He said they had been retrieved from an old sack, untouched since the era of the Cold War. But Prague police chief Martin Vondrasek told local radio that the weapons “have not gone through a registration process in the Czech Republic.”

A file photo of Palestinian ambassador to the Czech Republic Jamal Al Jamal, who was killed in an explosion in his residence in Prague-Suchdol, Thursday, January 1, 2014 (photo credit: AP/CTK, Krumphanzl Michal)

A file photo of Palestinian ambassador to the Czech Republic Jamal Al Jamal, who was killed in an explosion in his residence in Prague-Suchdol, Thursday, January 1, 2014 (photo credit: AP/CTK, Krumphanzl Michal)

Al-Jamal, 56, was killed Wednesday when a safe at his home exploded. He and his wife were at home at the time of the safe’s explosion, according to Palestinian Embassy spokesman Nabil El-Fahel. Al-Jamal was seriously injured and rushed to a hospital, where he was pronounced dead a short while later.

Palestinian Authority Foreign Minister Riad Malki said no foul play was suspected, and claimed that the safe had been left untouched for more than 20 years.

Later, however, El-Fahel told Czech radio that the safe had been in regular use. ”[The safe] was used on a daily basis at the embassy and it was opened and closed almost every day,” the embassy spokesman said.

The ambassador’s daughter, 30-year-old Rana Al-Jamal, told The Associated Press in a telephone interview from Ramallah in the West Bank that she thought foul play was involved.

“The Palestinian official account is baseless. The safe box has been in regular use — my mom (who lives there) told me that. The box was moved a day earlier and apparently something happened in the way,” she said.

“We, the family, believe it is a crime, and we need to find out what happened.”

She did not elaborate on what she thought may have occurred.

The safe was recently moved from the old embassy building, Malki had claimed, adding that it had come from a building that used to house the Palestinian Liberation Organization’s offices in the 1980s. “The ambassador decided to open it. After he opened it, apparently something happened inside (the safe) and went off,” Malki said.

Al-Jamal was born in 1957, in Beirut’s Sabra and Shatilla refugee camp. His family is originally from Jaffa in what is now Israel.

He joined Fatah in 1975. In 1979, he was appointed deputy ambassador in Bulgaria.

Starting in 1984, he served as a diplomat in Prague, eventually as acting ambassador. From 2005-2013, he served as consul general in Alexandria, Egypt.

In October 2013, he was appointed ambassador in Prague.

The Associated Press contributed to this report