Thousands of people lined up in Shanghai's largest property trading center in Pudong this weekend, following rumors the city will soon roll out even stricter policies on mortage down payments.

Over 2,300 home purchases were completed this past Saturday and Sunday, more than double the volume of the previous weekend. While the end of the month usually sees more home purchases anyway, rumors of new stricter home loan policies in September made more people eager to complete their home purchases as soon as possible.

Shanghai has been restricting second-home purchases since 2011 by requiring a downpayment of 60% of the purchase price. The minimum down payment for first homes remains relatively low, however, at only 30%. The new rumor says that amount will soon be increased to 50%. The city government information office said they could not comment on the reports.

Experts say that while the timing of such an announcement is not yet known, raising downpayment requirements would be logical given Shanghai's current housing market.

"Shanghai's property prices are still rising and there have been several months when the average home price was over 40,000 yuan per square-meter. If you want to curb rising prices, such polices are necessary. Current home buyers are trying to avoid the risk of policies that could possibly raise the down-payment. That means the market is moving in advance of the policy roll-out," Yan Yuejin, research director of E-House China R&D Institute.

Yan says that since more people will be trying to buy now to avoid a rise in downpayments, the market could actually cool a bit during the rest of year. Last week the the average Shanghai home sale price increased 4.89% from the previous week to 41,259 yuan per square-meter. That was first time in history the per-square-meter price broke above 41,000 yuan.