Japan’s new foreign minister has asked China’s government to provide a proper accounting of the facts in the stabbing death of a schoolboy in China last month, in a sign the new government in Tokyo will continue to push Beijing to explain the attack.

Japan wants an explanation as soon as possible, its new foreign minister, Takeshi Iwaya, told his Chinese counterpart Wang Yi in their first phone call, according to a statement from the Japanese government on Wednesday.

Despite repeated requests since the incident, the Chinese government hasn’t made clear the motives of the attacker. Iwaya told Wang that the uncertainty — alongside the arrests of Japanese nationals — was leaving Japanese nationals in China increasingly concerned.