The morning after election day, voters had learned the results of the presidential race — called once the president-elect received 270 electoral votes — and that Republicans had won control of the U.S. Senate.

But a week later, many House races are still too close to call.

The Associated Press surveys the numbers posted by local election officials and projects the winner using vote returns and other data. Races can be called within minutes of polls closing on election night. However, if a race has tight margins or an expected high volume of mail-in ballots, it can take longer to call.

This year, all 435 seats in the U.S. House of Representatives were up for election. According to the Cook Political Report’s House Ratings, 69 House races were competitive. Of those, 54 have been called.

Until the final races are called — eight of which are in California’s competitive congressional districts — control of the House remains unknown. In California’s 27th Congressional District race, Republican Rep. Mike Garcia conceded defeat on Monday, though the AP had not called the race by Tuesday morning.