China’s Semiconductor Manufacturing International Corp. used equipment from ASML Holding NV to manufacture an advanced processor for a Chinese smartphone that alarmed the US, according to people familiar with the matter.

In a suggestion that export restrictions on Europe’s most valuable tech company may have come too late to stem China’s advances in chipmaking, ASML’s so-called immersion deep ultraviolet machines were used in combination with tools from other companies to make the Huawei Technologies Co. chip, the people said, asking not to be identified discussing information that’s not public.