Investments in Charles Schwab Corp's "robo advisor" service grew to surpass $10 billion in September, more than double the year-ago level, a spokeswoman said Thursday.

The automated investment service, Schwab Intelligent Portfolios, allocates cash among exchange-traded funds according to formulas based on client questionnaires.

The San Francisco-based company previously reported the program's total assets stood at $4.1 billion at the same time in 2015 and at $8.2 billion at the end of the second quarter.

Demand for digital financial advice has drawn efforts to buy or build similar platforms by other companies, including Fidelity Investments and BlackRock Inc, the world's largest money manager, which acquired a robo service called FutureAdvisor in 2015.

Bank of America Corp. this month unveiled its own plans for a similar service called Merrill Edge Guided Investing.

Schwab makes Intelligent Portfolios available to clients directly and through the firm's affiliated third-party financial advisors. It launched the service in March 2015.

This article was provided by Reuters.