JAKARTA, Indonesia — Investigators on Wednesday broadened the possibilities of what may have contributed to the fatal crash of a Boeing 737 Max 8 last week, suggesting there were aircraft problems that may have played a role in the new plane’s nose-dive into the sea.

Boeing and aviation regulators in the United States, clearly worried that an unforeseen situation may have confronted the cockpit crew, also took steps on Wednesday to strengthen emergency procedures in the operations manual of the new plane, one of the most popular in commercial aviation.

The developments suggested that multiple causes may have combined to create a fatal cascade of problems for Lion Air Flight 610, which plunged into the Java Sea less than 15 minutes after takeoff on Oct. 29, killing all 189 people aboard.

Haryo Satmiko, the deputy chief of Indonesia’s National Transportation Safety Committee, said in an interview that he had held several discussions with Boeing officials after the crash about the possibility that inaccurate readings fed into the Max 8’s computerized system could make the plane enter a sudden, automatic descent.